Crocidolite

Crocidolite, a hydrous silicate of iron, sodium, and magnesium, occurring in fine, tough elastic fibres, like asbestos. It is of an indigo blue colour, and has a hardness of 4 and specific gravity, 3.2. In the Asbestos Mountains of Griqualand it occurs as an enclosure in quartz, forming the chatoyant mineral known as South African blue catseye. It is also in the same locality commonly more or less completely altered into a golden-brown limonite or hydrous iron-oxide, forming the brown and green catseyes. Unfortunately this beautiful mineral, now largely used for umbrella-handles, jewel-cases, and other small ornaments, has been tastelessly dyed a variety of hues.